1. Field of the Invention
The invention relates to a device for safely aligning the mouth of a sample container with the sample needle of a liquid sampling device.
2. Description of Related Art
The septum at the mouth of liquid sample containers must be precisely aligned with the sample needle to ensure that the septum is directly under the needle when the needle is inserted into the container. Typically, sample containers have a fair degree of dimensional tolerance and various manufacturers make containers, which hold the same volume, with different external dimensions. This tolerance makes precise alignment of the septum with the sample needle difficult and increases the likelihood of needle sticks.
U.S. Pat. No. 4,887,472 issued on Dec. 19, 1989 to Jansen discloses a closed loop sampler, which comprises a hood with an integrally formed sampling and venting needle. One end of the hood is thread mounted to a valve; the other end is mounted to a sliding sleeve, which receives a sample container sealed with a septum. The lower end of the hood is itself sealed with a septum. Samples are taken by sliding the sleeve with sample container upward towards the valve causing the two needles to penetrate the first septum which seals the hood, and then the septum of the sample container. The valve is then opened, and a sample is drawn. Upon completion of the sample draw, the sleeve is slid downward withdrawing the needles from the septum of the sample container as well as the septum of the hood. Sample needles may be cleaned before the next sample by circulating a wash fluid into the sealed area around the needles defined by the lower septum of the hood and the needles to flush away any traces of the old sample before a new sample is taken. One drawback to this invention is that should one or both of the sample needle or flush needle become clogged, it is necessary to replace the entire hood mechanism because of the integral formation of the sample and flush needles with the hood.
U.S. Pat. No. 5,604,320 issued on Feb. 18, 1997 to Boyd discloses a sampling apparatus with a ring insert and a shroud to guide the sample container. The ring insert of the Boyd patent is made to fit on the outside of the sample container and is removable from both the sample container and the shroud. Therefore each different type of sample container must have a corresponding ring insert. The need for a different ring insert to accommodate differences in sample container external dimensions complicates the task of retrieving a sample. If the proper ring insert is not available then manual alignment must be attempted. Further there is greater likelihood that the ring insert will be lost because the ring insert can be removed from the shroud.
Briefly described, the invention comprises two parts. First, is a cylindrical sleeve with two diametrically opposed slots cut into the sides and running along the sleeve axis. Second, is a guidance ring, which fits inside the sleeve and slides up and down on two diametrically opposed tabs which fit into the slots on the sleeve. The inside of the guidance ring is sized to accept the mouth of a sample container and the outside of the guidance ring is sized to fit inside the sleeve guide.
To operate the apparatus, the mouth of a sample container is inserted into the guidance ring, and the ring is slid up the sleeve until the sample needle pierces the septum. The guidance ring improves the alignment of the septum with the sample needle and reduces the likelihood of needle sticks because the sample container is held firmly in alignment with the sample needle.